1. Field of the Invention
The present invention relates to a power saving method and a related waveform-shaping circuit, and more particularly, to a power saving method and a related waveform-shaping circuit performing a time-division waveform-shaping function.
2. Description of the Prior Art
The advantages of a liquid crystal display (LCD) include lighter weight, less electrical consumption, and less radiation contamination. Thus, the LCD monitors have been widely applied to various portable information products, such as notebooks, PDAs, etc. The LCD monitor alters the alignment of liquid crystal molecules to control the corresponding light transmittance by changing the voltage difference between liquid crystals and provides images and produces gorgeous images with light provided by the backlight module.
Please refer to FIG. 1, which illustrates a schematic diagram of a prior art thin film transistor (TFT) LCD monitor 10. The LCD monitor 10 includes an LCD panel 122, a timing controller 102, a source driver 104, and a gate driver 106. The LCD panel 122 is constructed by two parallel substrates, and the liquid crystal molecules are filled up between these two substrates. A plurality of data lines 110, a plurality of scan lines 112 that are perpendicular to the data lines 110, and a plurality of TFTs 114 are positioned on one of the substrates. There is a common electrode installed on another substrate, and the voltage generator 108 is electrically connected to the common electrode for outputting a common voltage Vcom via the common electrode. Please note that only four TFTs 114 are shown in FIG. 1 for clarity. Actually, the LCD panel 122 has one TFT 114 installed in each intersection of the data lines 110 and scan lines 112. In other words, the TFTs 114 are arranged in a matrix format on the LCD panel 122. The data lines 110 correspond to different columns, and the scan lines 112 correspond to different rows. The LCD monitor 10 uses a specific column and a specific row to locate the associated TFT 114 that corresponds to a pixel. In addition, the two parallel substrates of the LCD panel 122 filled up with liquid crystal molecules can be considered as an equivalent capacitor 116.
The operation of the prior art LCD monitor 10 is described as follows. First, the timing controller 102 generates data signals corresponding to the images and a timing control signal and a clock signal corresponding control signals for the LCD panel 122. The source driver 104 and the gate driver 106 then drive different data lines 110 and scan lines 112 according to the signals sent by the timing controller 102, thereby turning on the corresponding TFTs 114 and controlling the voltage differences in the equivalent capacitor 11, and further changing the alignment of liquid crystal molecules and light transmittance. For example, the gate driver 106 outputs a pulse to the scan line 112 for turning on the TFT 114. Therefore, the voltage of the input signal generated by the source driver 104 is inputted into the equivalent capacitor 116 through the data line 110 and the TFT 114. The voltage difference kept by the equivalent capacitor 116 can then adjust a corresponding gray level of the related pixel through affecting the related alignment of liquid crystal molecules positioned between the two parallel substrates. In addition, the source driver 104 generates the input signals, and magnitude of each input signal inputted to the data line 110 is corresponding to different gray levels.
When the TFTs 114 is charged, the voltage drops from a high voltage level Vgh to a low voltage level Vgl on driving signals generated by the gate driver 106 causes a feed-through effect, which makes the voltage levels in pixels lower than it is supposed to be. If the voltage difference due to the feed-through effect is large, the flicker occurs while displaying. One solution to the flicker caused by the feed-through effect is to generate a shaped-waveform on the driving signals. The advantage of the shaped-waveform is that the feed-through effect can be reduced since the abrupt voltage drop from the high voltage level Vgh to the low voltage level Vgl becomes smaller.
However, the waveform-shaping circuit in the gate driver 106 works when the power supply thereof charges and discharges regulation capacitor in turns, which consumes a lot of power. Use of a power management chip to switch high voltage level on the driving signals would be an alternative. Still, the power consumption is inevitable since continuous charging and discharging the gate driver 106 is involved.